Alpha cleavage

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Alpha cleavage, in organic chemistry, refers to the act of breaking the carbon-carbon bond, where one of the carbons bears a functional group.

Generally this topic is discussed when covering GC/MS and occurs generally by the same mechanisms.

For example of a mechanism of alpha cleavage An electron is knocked off an atom (usually by electron collision) to form a radical cation. Electron removal generally happens in the following order. 1. Lone pair electrons 2. Pi Bond Electrons 3. Lastly - Sigma Bond Electrons

One of the lone pair electrons moves down to form a pi bond with an electron from an adjacent (alpha) bond.The other electron from the bond moves to an adjacent atom (not one adjacent to the lone pair atom) creating a radical. This creates a double bond adjacent to the lone pair atom (oxygen is a good example) and breaks/cleaves the bond from which the two electrons were removed.

Example C-C-(O::)-H > C-C-(O:.+)-H > C' + (C=O:+)-H where : is a lone pair + is a positive charge and ' is a radical/free electron

Closely related is beta cleavage, which is really just another application of alpha cleavage. Also McLafferty Rearrangement should be discussed.